1. Field of the Invention
The present invention relates to a cogeneration system in which both the electricity and waste heat generated from an engine are used, and, more particularly, to a cogeneration system which includes a separate outdoor heat exchanger to be heated by waste heat of an engine during a heating operation, thereby achieving an enhancement in heating performance.
2. Description of the Related Art
In general, cogeneration systems are adapted to generate both electricity and heat from a single energy source.
Such a cogeneration system can recover heat of exhaust gas or waste heat of cooling water generated from an engine or turbine during an electricity generation operation, so that the cogeneration system can achieve an increase in energy efficiency of 70 to 80% over other systems. By virtue of such an advantage, the cogeneration system has recently been highlighted as an electricity and heat supply source for buildings. In particular, the cogeneration system exhibits highly-efficient energy utilization in that the recovered waste heat is mainly used to heat/cool a confined space and to heat water.
FIG. 1 is a schematic configuration diagram illustrating a conventional cogeneration system.
As shown in FIG. 1, the conventional cogeneration system includes a gas engine 1, and a generator 3, which is driven by a driving force outputted from the gas engine 1, to generate electricity. The electricity generated from the generator 3 is used in a variety of devices including a cooling/heating unit 20, illumination devices, and other electrical products.
In the cogeneration system, waste heat generated from the gas engine 1, that is, heat of cooling water generated when the cooling water cools the gas engine 1, and heat of exhaust gas generated from the gas engine 1, is used during a heating operation of the cooling/heating unit 20.
Here, the cooling/heating unit 20 is of a heat pump type so that the cooling/heating unit 20 not only can be used as a cooling unit, but also can be used as a heating unit in a state in which the refrigerant flow direction in the refrigerant cycle is reversed. As in a general heat pump type configuration, the cooling/heating unit 20 includes a compressor 21, a four-way valve 23, an outdoor heat exchanger 25, an outdoor fan 26, an expansion device 27, and an indoor heat exchanger 29.
In particular, an air pre-heating heat exchanger 30 is arranged at the side of the outdoor heat exchanger 25 to preheat air passing around the outdoor heat exchanger 25 during a heating operation of the cooling/heating unit 20, using the waste heat of the gas engine 1.
In order to supply the waste heat to the cooling/heating unit 20, the cogeneration system also includes a cooling water heat exchanger 5 to recover the heat of the cooling water used to cool the gas engine 1, and an exhaust gas heat exchanger 9 arranged at an exhaust conduit 7 to recover the heat of the exhaust gas.
The cooling water heat exchanger 5 and exhaust gas heat exchanger 9 are connected to the air pre-heating heat exchanger 30 of the cooling/heating unit 20 by a heat transfer line 11, through which a heat transfer medium flows, so as to supply waste heat to the air pre-heating heat exchanger 30 during the heating operation of the cooling/heating unit 20. Thus, the cogeneration system recovers engine heat and exhaust gas heat, pre-heats outdoor air through the air pre-heating heat exchanger 30, using the recovered heat, and causes the pre-heated air to perform heat exchange with the outdoor heat exchanger 25, thereby preventing a degradation in the heating performance of the cooling/heating unit 20, which may occur when the temperature of the outdoor air is low.
When the cooling/heating unit 20 operates in a cooling mode, the flow path of the heat transfer medium is changed to communicate with a radiating line 13, which is connected to the heat transfer line 11, because it is unnecessary to supply waste heat. In this case, the waste heat is discharged to the atmosphere through a radiator 17, which includes a heat exchanger 15 and a radiator fan 16, or is supplied to and used in a water heater, a hot water supplier, or other systems.
In FIG. 1, reference character P designates pumps, each serving to force the heat transfer medium to flow through an associated portion of the heat transfer line 11, and reference character V designates valves, each serving to switch the flow path of the heat transfer medium between the heat transfer line 11 and the radiating line 13.
However, since the waste heat generated from the gas engine 1 is used only to pre-heat the outdoor heat exchanger 25 through the air pre-heating heat exchanger 30, the conventional cogeneration system has a limitation in enhancing the heating performance during the heating operation.